LibWebView+WebContent: Add an IPC to take an element screenshot

Author: https://github.com/trflynn89
Commit: 3c1c2994f1
Pull-request: https://github.com/SerenityOS/serenity/pull/15927
Reviewed-by: https://github.com/linusg ✅

Userland/Services/WebContent/WebContentServer.ipc

@@ -52,6 +52,7 @@ endpoint WebContentServer
     get_element_tag_name(i32 element_id) => (String tag_name)
     get_element_rect(i32 element_id) => (Gfx::IntRect rect)
     is_element_enabled(i32 element_id) => (bool enabled)
+    take_element_screenshot(i32 element_id) => (Gfx::ShareableBitmap data)
 
     webdriver_execute_script(String body, Vector<String> json_arguments, Optional<u64> timeout, bool async) => (Web::WebDriver::ExecuteScriptResultType result_type, String json_result)